Photonic Narrow Linewidth GHz Source Based on Highly Codoped Phosphate Glass Fiber Lasers in a Single MOPA Chain

We present the first demonstration of a fiber pumped source of coherent gigahertz (GHz) radiation based on parametric processes. The GHz source is compact, and pumped by two Q-switched highly codoped phosphate all-fiber lasers in a fusion-spliced master oscillator power amplifier chain at eye safe C-band wavelengths, with a GaSe crystal used for difference-frequency generation. The final stage used a novel highly codoped phosphate glass fiber that was only 12 cm long, and scaled the peak power of the narrow linewidth fiber laser to more than 4 kW. The generated GHz radiation at 270 GHz has a peak power of 48.1 muW, corresponding to a peak power spectral density of ~1.2 W/THz with an estimated linewidth of 40 MHz.